diff --git a/wcs/fields.py b/wcs/fields.py
index b59783302..2467ac158 100644
--- a/wcs/fields.py
+++ b/wcs/fields.py
@@ -2299,9 +2299,9 @@ class RankedItemsField(WidgetField):
             return ['']
         if type(value) is not dict:
             value = {}
-        items = value.items()
-        items.sort(lambda x,y: cmp(x[1], y[1]))
-        ranked = [x[0] for x in items if x[1] is not None]
+        items = [x for x in value.items() if x[1] is not None]
+        items.sort(key=lambda x: x[1])
+        ranked = [x[0] for x in items]
         return ranked + ['' for x in range(len(self.items)-len(ranked))]